Mandrel



March 12, 1929. T. D. CRAIG MANDREL Filed oct.' 51, 1927 lNvENToR 7 o//zCruL/y ATTORNEY o a e9 alnl 3 2 5 2 vl Patented Mar. 12, 1929.

`lLI-IOIVLAVS D. CRAIG, OF LOS ANGELES., CALIFORNIA.

MANDREL.

Application filed October- 31, 1927. Serial No. 230,010.

My invention relates generally to mandrels and more specifically to a mandrel particularly adapted, although not necessarily, for

use in dentistry, in support-ing a disk of abrasive material, the mandrel being inserta- Y ble into the chuck of the hand piece of a dent-al engine for clamping thereof by the chuck,

so that when the engine is in operation, the

mannrel and disk will be rotated tothereby permit grinding operations to be performed on the teeth; all of which is well known in the art and will be understood.

A well known form of mandrel of the above described character' comprises a pair of telescopically associated members in which the inner member is in the form of a pin insertabile into the outer member constituting a sleeve, the members having co-acting heads adapted to engage opposite sides of a disk through the center of which the pin extends,

to the end that the disk will be supported on the mandrel at right angles to the axis of the latter. ,For the purpose of retaining the pin against displacement from the sleeve it is bent or undulated longitudinally, and reliance is placed on the frictional engagement of the undulations with the inner wall of the sleeve to retain the pin in the latter. It has been found in practice that this method of retaining the pin is extremely unreliable and that the pin frequently loosens and works out of the sleeve during the grinding operation,

thus causing loss of time as well as subjecting the patient to the danger of injury by the disk.

It is a purpose of my invention to provide a mandrel which embodies extremely simple means responsive to clamping of the mandrel in the clutch of the hand piece to cause the inner member of the mandrel to be positively retained against displacement from the outer l member and the inner member to be firmly supported so as to insure the true and even running of the disk, thus greatly facilitating the work of the dentist and entirely eliminating the danger of injury to the patient as a result of displacement of the inner member.

I will describe only one form of mandrel embodying my invention and will then point out the novel features in claim.

In the accompanying drawing Fi 1 is a view showing in side elevation one iorm of mandrel embodying my invention, applied to the hand piece of a dental en- F ig. 2 is anv enlarged vertical sectional view taken on line 2 2 of Fig. 1 and looking in the direct-ion of the arrows; and

Figf?, is an enlarged sectional view taken on the line 3-.3 of Fig. 1 and looking in the 60 direction of the arrows.

Referring specifically tothe drawing in which similar reference lcharacters designate similar parts in each of the several views, my i invention in its present embodiment Scomprises a pair of members designated generj ally at M and M', and capable of being telescopically associated with each other, the for mer being in the form of a sleeve 10 and ofA uniform diameter and enlarged at one end to provide a circular head 11 having a plurality of prongs 11a projecting from the outer side thereof, while the latter member is in the form of a pin 12 of such diameter as to have a sliding lit within the sleeve so as to permit its being readily unserted or withdrawn, the pin 12 being rovided with a circular head 13. The mandi-e as above described is adapted to support a disk 15 of abrasive material such as sandpaper, provided with a central open-A ing through which the pin 12 is adapted to be extended. With the disk placed on the pin,

the latter is inserted into the sleeve until the disk is clamped between the heads 11 and 13, at which time the prongs 11a will pierce the disk and thus lock the disk to the sleeve for rotary movement therewith. v

The mandrel with the disk 15 supported thereon is adapted to be inserted into the jaws 16 of the clutch 17 of a conventional form of hand piece 18 constituting part ofa dental engine (not shown) such asis com-- monly used in dental laboratories to provide the necessary power for driving various forms of tools clamped in thechuck 17. The jaws 16 are adapted to be contracted to clampingly engage the sleeve 10 by means of a contracting element 19 mounted in the housing 2O of the hand piece 18 andbearing against the tapered upper end of the jaws, the element co-operatingwith the tapered lower end of the housing 20 bearing againstthe similarly tapered lower end of the jaws, to contract the latter from both ends as the element is forced downwardly by a manually 105 operable feed screw 21, all of which is conventional and will be understood.

Y For the purpose of retaining the pin 12 against displacement from the sleeve 10 when the latter is clamped in the jaws 16, the sleeve 1.710

is preferably rendered constrictable,.and to this end, the Wall of the sleeve, in the present instance, is provided With longitudinally eX- tending and diametrically opposite slots 22p, the slots being spaced from the ends of the sleeve and providing therebetween, fleXibie portions 23. It Will be clear that when the jaws 16 are contracted to clampingly engage the sleeve they will simultaneously constrict the portions 23, thus flexing the latter in- Wardly into clamping engagement with the pin 12, so that th'e pin Will be iirnily gripped in the sleeve against displacement therefrom. The clamping action of the chuck is thus caused to perform the dual function of preventing displacement of both the sleeve and the pin from the chuck. Furthermore as the pin is firmly supported axially Within the sleeve, the true and even running of the disk is insured at all times, thus greatly facilitatingy the Work of the dentist.

Although I have herein shown and de scribed only one form of mandrel embodying my invention, it is to be understood that various changes and modifications may be made therein Without departing from the spirit of the invention and the spirit and scope of the y points to provide portions capable of beingv flexed inwardly in response to the constricting action of a clutch upon said portions sov as to engage and grip the inner member and thereby prevent displacement of the latter from the outer member7 the slots terminating in spaced relation to both ends ot the outer member so that the Wall of the outer meinber at its ends remains unbroken and rigid to insure that the mandrel Will be rigidly supported centrally in the chuck.

THOMAS D. CRAIG. 

